A012233 arctan(arctan(arctanh(x)))=x-2/3!*x^3+32/5!*x^5-944/7!*x^7+64640/9!*x^9...

1, -2, 32, -944, 64640, -5881600, 919673856, -172830523392, 48225099218944, -15466881283850240, 6745794347282989056, -3302151520495305490432, 2072514460288282576027648, -1438958551527596730993344512

Offset

0,2

Links

Table of n, a(n) for n=0..13.

Mathematica

With[{nn=30}, Take[CoefficientList[Series[ArcTan[ArcTan[ArcTanh[x]]], {x, 0, nn}], x] Range[0, nn-1]!, {2, -1, 2}]] (* Ray Chandler, Nov 28 2016 *)

Crossrefs

Sequence in context: A202408 A069182 A333772 * A321712 A211488 A012119

Adjacent sequences: A012230 A012231 A012232 * A012234 A012235 A012236

Keyword

sign

Author

Patrick Demichel (patrick.demichel(AT)hp.com)

Status

approved